A more reliable, technique-insensitive and durable adhesive resin bond to dentin is required if the full benefit of bonded restorations is to be realized. This is especially important due to the fact that caries remains a major health problem, dentin sensitivity affects greater than 40 million Americans, and root caries is increasing with our aging population. Adhesive bonding to enamel has proven to be highly successful; however, bonding to dentin remains poorly understood and unreliable. Resin adhesion to dentin is thought to be primarily micromechanical by the interdiffusion of adhesive monomers into the acid demineralized organic matrix; through steps not dissimilar to any other adhesive procedure, i.e. surface preparation, wetting and solidification. The long-range goal of our program of research is the conservative restoration of teeth, prevention of demineralization, and desensitization of exposed dentin surfaces through dentin bonding. The specific objective of this application is to identify resin-dentin bond degradation involved with the wetting process. The central hypothesis of this work is that the mineral depleted dentin surface must be completely and homogeneously infiltrated by the adhesive system for a successful dentin bond. Preliminary mechanical, fractographic and analytical work provide evidence that current dentin adhesive systems incompletely infiltrate the dentin surface, phase separate, polymerize sub-optimally, and hydrolytically degrade, leading to clinical restorative failure. The rationale for the proposed research is that, once mechanisms of dentin bond formation and failures are understood, evidence-based novel approaches for successful dentin adhesion can be developed. Aim 1 will determine probability failure rates and debond pathways of the dentin-resin composite bond exposed to simulated bacterial and tissue inflammatory responses utilizing a novel accelerated aging model. Aim 2 will identify the resin monomer degradation products from the storage media from Aim 1. Aim 3 will identify resin infiltration and stability throughout the hybrid layer using micro-Raman spectroscopy. We expect to demonstrate a decrease in bond strength, a changing debond pathway and a decreasing amount of adhesive monomer in the hybrid layer. This study is significant, because the knowledge gained will improve the understanding of dentin adhesion and biodurability; leading to hypothesis-driven clinical trials examining the wetting conditions required for a clinically successful dentin bond.